Secure real-time transport protocol (sRTP) defines a profile of RTP intended for secure communication of RTP data. Interworking between protocols, such as H.323 and session initiation protocol (SIP) is provided for basic connections. However, when supplementary services, such as call transfers and forwards, are needed, inefficiencies result when using sRTP. For example, a first device may send a call request for a second device. The call request includes a first key and is forwarded with the first key to the second device. If a supplementary service is required, such as transferring the call a third device, then the first key cannot be used to send a call request to the third device. This is because the second device already knows the first key and thus it would not be secure to send it to the third device. Accordingly, the first device is contacted again for it to generate a third key. Thus, the first device sends another message with a second key. The call request is then forwarded to the third device with the second key.
The above process is inefficient in that it requires additional messaging with the first device to have it generate the second key. This uses valuable bandwidth. Also, additional delays are introduced in a call because the first device needs to be contacted again and a response needs to be received from the first device, in order to forward the call request to third device.